1. Field of the Invention
The present invention relates to overheat prevention for a portable telephone, more particularly, to a method and apparatus for calculating data transmission time to calculate a temperature of a device expected after data transmission based on the calculated data transmission time, thereby making it possible to previously determinate whether the temperature of the device exceeds a set temperature before starting transmission.
2. Description of the Related Art
FIG. 1A and FIG. 1B show an example of a prior art method of providing thermal protection for a communication device. This method is disclosed in Japanese Patent Publication No. 38594/95.
FIG. 1A is a block diagram showing a primary portion comprising communication device 1; microcomputer 2 for controlling communication device 1; and temperature sensor 3 for detecting a temperature of radiator 4 attached to a power amplifier of communication device 1. As shown in FIG. 1B, conventionally, when a temperature of the device exceeds temperature reference value T.sub.U, transmission is limited and even emergency transmission can not be performed. This example, however, newly provides reference value T.sub.H to allow transmission only for a very short time even when the temperature exceeds T.sub.U. In this point, this example differs from the present invention in its object and thus provides a different content from the present invention.
Besides the above-mentioned example, the following known examples of the prior art relating to this field are disclosed.
Japanese Patent Laid-open Publication No. 177055/95 PA1 Japanese Patent Laid-open Publication No. 5411/97 PA1 Japanese Patent Laid-open Publication No. 214363/97
When a portable telephone is used to transmit data, a TDMA (Time Division Multiple Access) system is conventionally utilized as a data transmission scheme to use only one of three slots in one frame as a transmission slot, thereby presenting a limit of a maximum transmission speed of 9.6 kbps.
In this case, since two of the three slots in one frame are not used for transmission, a temperature rise of the power amplifier is slow to thereby enable the temperature rise of the device to be sufficiently prevented with a countermeasure such as heat radiation from the power amplifier to a panel. However, associated with data transmission at a higher speed, the transmission speed is increased at as high as 28.8 kbps using a packet communication. This is achieved by a scheme in which three slots in one frame are used as transmission slots, which means that the power amplifier always operates.
Thus, the temperature rise is increased and can not be dealt with by the conventional heat radiation method. Conventionally, this temperature rise has been dealt with by a method of adding a plate for heat radiation to the device to release heat to the outside, or of improving heat resistance of electronic components. However, it is desired to avoid releasing heat by adding the plate for heat radiation as much as possible due to the need for a reduction in cost and weight of the device. On the other hand, the improvement in heat resistance of electronic components has a disadvantage of requiring time and cost to make it impossible to provide immediate countermeasures.